Glycerol triether lubricant compositions



United States Patent Ofiice 2,841,479 Patented July 1, 1958 GLYCEROL TRIETI-IER LUBRICANT COMPOSITIONS Robert E. Hefner and Malcolm E. Pruitt, Lake Jackson,

Tex., assignors to The Dow Chemical Company, Midland, Mich., a corporation of Delaware No Drawing. Application May 28, 1954 Serial No. 433,256

9 Claims. (Cl. 44-58) This invention relates to lubrication. More specifically, the present invention relates to novel internal combustion engine fuels, especially spark ignition engine fuels, and to a method for lubricating and increasing the performance characteristics of said engines.

According to this invention, it has been found that certain trialkyl triethers of (monohydroxy polyoxyalkylene) monoethers of glycerol are excellent lubricants for dissolution in internal combustion engine fuels. It has also been discovered that when these glycerol trialkyl triether compounds are dissolved in liquid hydrocarbon fuels being fed to internal combustion engines, especially spark ignition engines, they are surprisingly effective in increasing engine performance and in controlling wear, corrosion, and contamination of the engine.

The trialkyl triethers of (monohydroxy polyoxyalkylene) monoethers of glycerol which may be employed in the present invention are normally liquid compounds, the polyoxyalkylene chains of which are composed of at least 5 oxyalkylene units. These compounds correspond to the general formulae:

wherein R R and R are alkyl groups and may be the same or different; 11 has an average value of from 2.5 to 4.0 inclusive; and x has a value of at least 5.

Suitable glycerol triether compounds are those having polyoxyalkylene chains composed entirely of polyoxypropylene or polyoxybutylene units. Other suitable glycerol triether compounds are those having mixed polyoxyalkylene chains formed randomly from at least two different alkylene oxides of the class consisting of ethylene oxide, 1,2-propylene, 1,2-butylene oxide, and 2,3-butylene oxide, e. g. mixed oxyethylene-oxy-1,2-propylene chains, mixed oxyethylene-oxy 1,2 butylene chains, mixed oxy-1,2-propylene-oxy-2,3-butylene chains, mixed oxyethylene-oxy-l,Z-propylene-oxy 1,2 butylene chains, etc. When oxyethylene units are present in the mixed polyoxyalkylene chain, however, they should constitute no more than 50 mole percent of the total oxyalkylene units. Since these polyoxyalkylene ether chains can and do vary in length from molecule to molecule in any given reaction product, the compounds herein described are best defined in terms of their average molecular Weights or according to the average number of oxyalkylene units in the polyoxyalkylene ether chain, usually from 5 to about 50 oxyalkylene units.

Highly desirable glycerol trialkyl triether compounds for use in accord with the present invention are the trialkyl triethers of (monohydroxy mixed polyoxyalkylene) monoethers of glycerol disclosed and claimed in our e pending application Serial No. 433,255. These novel compounds have mixed polyoxyalkylene chains which may be attached to either the middle or the terminal carbon atom of the glycerol nucleus. The polyoxyalkylene chains are composed of from 5 to about 50 oxyalkylene units and are formed randomly from two or more alkylene oxides each containing less than 5 carbon atoms per molecule, viz. ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, and 2,3-butylene oxide. Of the oxyalkylene units in the mixed polyoxyalkylene chains, those corresponding to any single alkylene oxide may not constitute more than 90 mole percent of the polyoxyalkylene portion of the molecule, nor may oxyethylene units comprise more than 50 mole percent thereof. Typical of these new trialkyl triethers of (monohydroxy mixed 7 polyoxyalkylene) monoethers of glycerol are those which correspond to the following general formula:

wherein R R and R are alkyl groups having from 1 to 8 carbon atoms each, said alkyl groups being either primary or secondary alkyl groups which may be the same or dilferent; n is an integer from 2 to 3; and y+z represents the average number of all oxyalkylene units in the molecule, said average number having a value from 5 to 50 of which y constitutes from 10 to 50 mole percent of the total when n is 2 and from 10 to mole percent of the total when n is 3. Usually the alkyl groups attached to these compounds are lower alkyl groups having no more than 4 carbon atoms each.

The liquid trialkyl triethers of (monohydroxy polyoxyalkylene) monoethers of glycerol in accord with the invention, especially those having mixed polyoxyalkylene ether chains, possess low pour points (e. g. below 50 F.), high flash points (e. g. above 370 F.), and high viscosity indices (e. g. above 14-0). The viscosities of these compounds vary from about 2.5 to 15 centistokes and higher at 210 F. depending upon the average number of oxyalkylene units in the polyoxyalkylene chains.

A large proportion of oxyethylene units to oxypropylene or oxybutylene units will ordinarily impart a high degree of thermostability to those glycerol triether compounds having mixed polyoxyalkylene chains. Water miscibility will at the same time be increased at the expense of'their miscibility in liquid hydrocarbons. On the other hand, a large proportion of oxypropylene or oxybutylene units will increase the liquid hydrocarbon miscibility and decrease the water miscibility of these compounds, oxybutylene units even more than oxypropylene units. Thermostability, however, decreases with increasing number of oxybutylene units in the polyoxyalkylene chains. The presence of three alkyl groups in the instant compounds enhances their miscibility with petroleum oils and liquid hydrocarbon motor fuels, e. g. gasoline.

In addition to miscibility with liquid hydrocarbons, these unique compounds have good lubricity and are capable of being spread into thin films which have good strength under heavy loads and high shear. Due to their good thermostability and low rate of change in viscosity with increasing temperature, these glycerol triether compounds may be employed as lubricants in internal combustion engines by interposing them between relatively moving engine surfaces.

The normally liquid glycerol trialkyl triether compounds in accord with the invention are also very effective as lubricants when added to liquid hydrocarbon motor fuels and fed to internal combustion engines. In such use, these novel compounds show little tendency to break down and form acids, lacquers, or sludges, or to deposit out as carbon in the combustion chambers. When the gasoline motor fuel also contains tetraethyl lead fluid, the glycerol trialkyl triether compounds of the invention materially reduce or entirely prevent lead salts from depositing out in the engine, e. g. on the walls of the combustion chamber. These glycerol triether compounds may also be employed to minimize crankcase dilution in 4-cycle engines by helping to keep gasoline, water, lead salts, etc. from dropping into the crankcase from the combustion chamber. Quite surprisingly, these glycerol triether compounds when dissolved in liquid motor fuels and fed to internal combustion engines exert a solvating actionon pie-formed carbon deposits, gums, and sludges. They also minimize wear, corrosion, and contamination of the engine, and at the same time increase the overall performance of the engine, e. g. increase engine efficiency, decrease fuel consumption, etc.

In such use, a small though eifective proportion of at least 0.1 percent by volume of the glycerol triether compound is dissolved in the liquid hydrocarbon motor fuel, e. g. gasoline. When dissolved in gasoline and fed to a 4-cyclc spark ignition engine, from 0.1 to 2 percent by volume of the glycerol triether compound is usually satisfactory. A somewhat higher concentration of the glycerol compound within the range of l to 20 percent and ordinarily from 5 to 12 percent by volume is dissolved in the motor fuel when the latter is to be fed to Z-cycle engines such as outboard motors. Engine contamination can not only be prevented or effectively controlled, but in many cases, preformed carbon deposits can be removed or reduced in amount by admixing a small though effective proportion of the glycerol triether compound with a conventional petroleum oil lubricant and adding the resultant lubricating mixture to the motor fuel being fed into the engine.

Remarkably good fuel efiiciency is obtained in a 2- cycle engine such as an outboard motor when approximately 5 volume percent of a glycerol triether compound of the invention is added to the gasoline motor fuel. When employing such compositions in extensive 2-cycle engine tests, almost no spark-plug fouling was encountered. Furthermore, an examination of the motor after testing showed good lubrication with little if any wear on the pistons, rings, and crankshaft bearings. The combustion chamber, intake ports, and manifold were almost completely devoid of deposits. The following examples illustrate but do not limit the invention.

EXAMPLE 1 This example describes the preparation and properties of one of the new trialkyl triethers of (monohydroxy mixed polyoxyalkylene) monoethers of glycerol employed in the invention.

A 100 gallon, steam-jacketed, steel reaction vessel was purged with dry nitrogen and charged with 25 U. S. gallons of toluene and 4.41 pounds (0.192 pound mole) of sodium metal. The contents of the vessel was then mixed with a mechanical stirrer and heated to about 110 C. Thereupon the pressure was bled down to 30 pounds per square inch gauge and exactly 23 pounds (0.192 pound mole) of glycerol-1,3-dimethyl ether was slowly added to the thoroughly-mixed contents of the vessel while maintaining the pressure in the range of 30 to 50 pounds per square inch gauge. After adding all of the glycerol-1,3-dimethyl ether, the reaction mixture was digested for approximately two hours until essentially all of the glycerol-1,3-dimethyl ether had been reacted to form the sodium derivative thereof as evidenced by cessation in the evolution of hydrogen gas. The temperature of the well-agitated contents of the reaction vessel was then raised to 125 C. and 469.5 pounds of 4. an alkylene oxide mixture consisting of 55.5 pounds (1.26 pound moles) of ethylene oxide and 414 pounds (7.13 pound moles) of 1,2-propylene oxide was added at such a rate that the pressure was regulated between 30 and 50 pounds per square inch gauge to maintain the temperature at approximately 125 C. This alkylene oxide addition represents a reactant ratio of 6.56 pound moles of ethylene oxide and 37.14 pound moles of propylene oxide per pound mole of glycerol-1,3-dirnethyl ether. After the addition of all the mixed alkylene oxides, the reaction mixture was digested for about 30 minutes. Methyl chloride was then passed into the reaction vessel in excess of the amount of sodium initially charged in order to cap, i. e. etherify, all of the polyoxyalkylene chains. After again digesting the reaction mixture to insure completeness of the reaction, the total product was filtered while hot to remove sodium chloride and heated under vacuum to distill otf toluene and low boiling fractions. The purified triether of glycerol was found to have the, following physical properties:

Average molecular weight (by hydroxyl analysis of uncapped material) 1090 Flash point (C. O. C.) F 420 Viscosity at F centistokes 5 4.4 Viscosity at 210 F do-.. 9.84 Viscosity index 145 1 A. S. T. M. standard method D567-41.

The viscosity index is an empirical number indicating the effect of change of temperature on the viscosity as calculated from viscosity at 100 and 210 F. A high viscosity index, e. g. 145, signifies relatively small change That the glycerol trialkyl triether products of the invention have oxidation resistance which compares favorably with marketed petroleum oils is shown by the results of the accelerated oxidation tests hereinafter described.

These tests were conducted in a glass cell containing a 200 grams sample of the liquid to be tested and, in addition, a uniformly polished and weighed copper strip. The glass cell with its contents was then placed in a constant temperature bath heated to 135 C. and air, saturated with water vapor, was bubbled through the test-liquid at a rate of 100 milliliters per minute. At the end of hours, the liquid was analyzed for increase in viscosity, increase in acidity, copper content, and amount of sludge.

Two tests were carried out on samples of a glycerol trialkyl triether product in accord with the invention prepared according to the general procedure of Example 1 and using a reactant ratio of 8.5 pound moles of ethylene oxide and 25.4 pound moles of 1,2-propylene oxide per pound mole of glycerol-1,3-dimethyl ether. One sample (A) of the liquid product was stabilized with 0.6 percent by weight of phenothiazine and the other sample (B) with 1 percent of alpha-naphthylamine.

For purpose of comparison, two liquids (C) and (D) not in accord with the invention were also subjected to the above-described accelerated oxidation test. The liquids tested were premium grade motor oils both of which were especially recommended and sold byt he manufacturer as crankcase lubricants for 4-cycle engines. Oil C was a synthetic oil of the polyoxyalkylene glycolether type stabilized with approximately 4 percent by weight of alpha-naphthylamine. Oil D was a highly re fined paraffin-base oil which, as purchased, contained about 15 percent by weight of viscosity index improvers of which approximately one half were polyacrylic' esters.

Th esult of all f tests are ound i able senate Table I Acidity Viscosity copper Sludge Liquid Tested Increase, Increase, Content, Content,

p. p. :11. percent p. p. m. wt.

percent EXAMPLE 3 This example compares four glycerol trialkyl triether compounds of the invention with two petroleum oils as motor fuel additives for Z-cycle spark ignition engines.

In testing each additive, one U. S. gallon of the additive was dissolved in 16 U. S. gallons of regular gasoline containing tetraethyl lead fluid and the resultant solution was fed as fuel to a 2-cycle twin-cylinder 7.5 horsepower Evinrude outboard motor. Before each test run, the motor was carefully cleaned. Special attention was given to the combustion chamber, exhaust manifold, intake port, and piston ring area. A new set ofspark plugs was used for each run. The motor was run continuously at approximately 3,000 revolutions per minute in a sea-water flume until all 17 gallons of the fuel additive mixture had been consumed. The time required to consume the 17 gallons of test fuel was recorded, viz. the running time.

One test run was carried out using as the additive to gasoline, the glycerol trialkyl triether produce (E) of Example 1. Three additional test runs were carried out employing other glycerol trialkyl triether products of the invention prepared according to the general pro cedure of Example 1. The reactant ratios employed in preparing the four glycerol trialkyl triether products tested are listed in Table II. The physical properties of these four glycerol trialkyl triethers are contained in Table III.

Table II Glycerol Trialkyl Triether Reactant Ratio of the Glycerol-1,3-Dialkyl Capping Ether to the Alkylene Oxides Agent 1 mole of glycerol-1,3-dimethyl ether to 6.56 moles of ethylene oxide and 37.14 moles of 1,2-propylene oxide.

1 mole of glycerol-1,3-dimethyl ether to 8.49 moles of ethylene oxide and 25.42 moles of 1,2propylene oxide.

1 mole'oi glycerol-1,3-diethyl ether to 22.8 moles of ethylene oxide and 22.8 moles of Lil-propylene oxide.

1 mole of glycerol-1,3-dibutyl ether to 3.53 moles of ethylene oxide and 31.81 moles of 1,2- and 2,3-butylene oxides.

Methyl Chloride.

Ethyl Chloride.

Methyl Chloride.

Table III Glycerol Trialkyl Triether Flash Point (O. 0. 0.), F.

Average Molecular Weight 1 Viscosity in cks. at 100 F Viscosity in cks. at

Viscosity 210 F.

Index I Following each test run, the motor was dismantled and inspected. The combustion chamber and the area around the intake and exhaust ports were checked for carbon deposits and for the deposition of lead salts. The cylinder walls and piston skirts were checked for varnish. The lubrication of the engine was rated according to the amount of lubricant present on the piston surfaces, ring grooves, and crankshaft bearings. These observations are all contained in Table IV which also gives the running time required to consume exactly 17 gallons of the additive-containing gasoline, running time being a good measure of engine etficiency.

. Table IV Carbon Run- Lubrl- Varnish Lubrlconing cant Combus- Intake Exhaust tion Time, tion Ports Ports hours Chamber Clean..- Llght Excellent. 22.5 -do. do ..do.- 22.3 do None.-.. ...---do 22.7 do..--- .do do.-- 22.6 Medium. Light-.. Fair 19.1 Heavy Medium. Poor 17.8

1 Lead salts found around the exahust ports.

EXAMPLE 4 This example further compares the same four glycerol trialkyl triether compounds and one of the petroleum oils employed in Example 3 as motor fuel additives for 2- cycle spark ignition engines.

These tests were carried out according to the same general procedure outlined in the preceding example except that the engines were run at 1000 revolutions per minute for a period of 36 hours with spark suppressors of approximately 12,000 ohms, resistance on the spark plugs.

Table V lists the additives employed and gives the results for each test as follows: the condition of the combustion chamber, the amount of varnish on the cylinder walls and piston skirts, the lubrication rating for the engine in accord with the amount of lubricant present on the piston surfaces, ring grooves, and crankshaft bearings, and finally, the number of plugs which fouled during the 36-hour test run. The additives used in these tests are identical with those characterized under the same letter designations in Example 3, additives E, F, G, and H being glycerol trialkyl triethers in accord with the invention and additive I being an outboard motor oil not in accord with the invention.

proportion of from 0.1 to 20 percent by volume of a mixture of normally liquid trialkyl triethers of (terminal monohydroxy polyoxyalkylene) monoethers of glycerol, said alkyl groups being the same or different. and having from 1 to 8 carbon atoms each, and said polyoxyalkylene monoether groups being composed of an average of from 5 to 50 oxyalkylene units formed from at least one alkylene oxide selected from the class consisting of ethylene oxide, 1,2-propylene oxide, 1,2-buty1ene oxide, and 2,3- butylene oxide.

2. A spark ignition. engine fuel consisting essentially of gasoline containing from 0.1 to 20 percent by volume of a ,mixture of trialkyl trietliersof (terminal monohydroxy mixed polyoxyalkylene):monoethers of glycerol, said alkyl groups being the same .or, different and having from 1 to 8 carbon atoms each, and said mixed polyoxyalkylene monoether groups being composed of an average of from about to about 50 oxyalkylene units and formed randomly from at least two different alkylene oxides selected from the class consisting of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, and 2,3- butylene oxide, no one oxide of which may form more than 90 mole percent and ethylene oxide no more than 50 mole percent of the total oxyalkylene units in the polyoxyalkylene portion of the molecule.

3. An engine fuel according to claim 2 wherein the mixed polyoxyalkylene monoether groups are attached to the middle carbon atom of the glycerol nuclei.

4. An engine fuel according to claim 3 wherein the polyoxyalkylene monoether groups consist of oxyethylene and oxy-1,2-propylene units.

V 5. An engine fuel according to claim 4 wherein the alkyl groups contain from 1 to 4 carbon atoms.

6. An engine fuel according to claim 5 wherein the mixed polyoxyalkylene monoether groups contain an average of from to 30 oxyalkylene units.

7. An engine fuel according to claim 6 wherein the alkyl groups are methyl.

8. A liquid hydrocarbon motor fuel for internal combustion engines consisting essentially of gasoline and containing from 0.1 to percent by volume of a mixture of normally liquid trialkyl triethers of (monohydroxy polyoxyalkylene) monoethers of glycerol corresponding to at least one of the general formulae:

8 wherein R R and R are alkyl groups, said alkyl groups being the same or different and having from 1 to 8 carbon atoms each; n has an average value of from 2.5 to 4.0 inclusive; and x has a value of from 5 to inclusive. 9. A. spark ignition engine fuel consisting essentially of gasoline containing from 0.1 to 20 percent by volume of a mixture of trialkyl triethers of (monohydroxy mixed polyoxyalkylene) monoethers of glycerol corresponding to the general formula:

CHz-O R1 CHr-OR: wherein R R and R are alkyl groups having from 1 to 8 carbon atoms each, said alkyl groups being independently selected from the class consisting of primary and secondary groups; n is an integer from 2 to 3; and y+z represents the average number of all oxyalkylene units in the molecule, said average number having 'a value from 5 to 50 of which y constitutes from 10 to 50 mole percent of the total when n is 2, and from 10 to mole percent of the total when n is 3.

References Qited in the file of this patent UNITED STATES PATENTS 2,184,956 Gilliland et al. Dec. 26, 1939 2,563,101 Colwell et al. Aug. 7, 1951 2,733,272 Horsley et a1. Jan. 31, 1956 

1. A LIQUID MOTOR FUEL FOR INTERNAL COMBUSTION ENGINES CONSISTING ESSENTIALLY OF GASOLINE AND CONTAINING A MINOR PROPORTION OF FROM 0.1 TO 20 PERCENT BY VOLUME OF A MIXTURE OF NORMALLY LIQUID TRIALKYL TRIETHERS OF (TERMINAL MONOHYDROXY POLYOXYALKYLENE) MONOETHERS OF GLYCEROL, SAID ALKYL GROUPS BEING THE SAME OR DIFFERENT AND HAVING FROM 1 TO 8 CARBON ATOMS EACH, AND SAID POLYOXYALKYLENE MONOEHTHER GROUPS BEING COMPOSED OF AN AVERAGE OF FROM 5 TO 50 OXYALKYLENE UNITS FORMED FROM AT LEAST ONE ALKYLENE OXIDE SELECTED FROM THE CLASS CONSISTING OF ETHYLENE OXIDE, 1,2-PROPYLENE OXIDE, 1,2-BUTYLENE OXIDE, AND 2,3BUTYLENE OXIDE. 